Although brash T-Mobile CEO John Legere may have set off another flame war with his final dig at BlackBerry CEO John Chen.

It was T-Mobile Chief Marketing Officer Mike Sievert who played the role of peacemaker, and introduced in a blog post an offer of a $200 credit toward a new device when you trade in a working BlackBerry at T-Mobile. Customers who want to upgrade to a BlackBerry Z10 or BlackBerry Q10 can get an additional $50 off the purchase price.

The $200 offer is particularly rich considering many of the old BlackBerrys that would be traded in aren't worth much on the secondary market.

Sievert's efforts may be wasted. Legere couldn't help but mock Chen for not being on Twitter, adding that he would "check MySpace." While it may have been an innocent joke, the image of a company that faded away probably rubbed the leader of BlackBerry the wrong way.

Was going to engage John Chen on Twitter, but turns out he's not here. I'll check MySpace. Don't worry @BlackBerry Something in the works!

T-Mobile initially set off the fireworks with an e-mail campaign prompting customers to dump their BlackBerrys in favor of an iPhone. That, in turn, rallied faithful BlackBerry users into tweeting Legere with the hash tag #CHOOSEBLACKBERRY10.

"I can assure you that we are outraged too," he wrote. "What puzzles me more is that T-Mobile did not speak with us before or after they launched this clearly inappropriate and ill-conceived marketing promotion."

Chen has the Herculean task of reviving BlackBerry, which last year saw its market share nearly vanish and customers shun its products despite a splashy launch of its next-generation operating system and smartphones. Chen is trying to push BlackBerry more into services and businesses without completely abandoning the consumer market, but faces many obstacles.